I put together a spreadsheet with eleven midranges for a Unity horn / waveguide.

It's on Google Docs, so you guys are welcome to add to it.

So far the two best candidates are the LA6-MR from Eminence and the JBL 400GTI.

I came up with a scoring system too. Basically 532 is a perfect score, and anything above or below that isn't quite perfect. John Sheerin's driver gets a perfect score, bracketed by the JBL 400GTI and the LA6-MR. The Beyma 5G40ND and the Ciare 6.38 NdMR look sharp too.

Originally posted by omarmipi Awesome! I got a value of 491Hz with the Audax HM100C0 drivers that I am currently using. I am not sure if the 54Hz Fs matters though. The motor on this thing is freakishly large too.

Nice one! I'll have to look that up.

I found another good & cheap candidate. The TangBand W2-880 scores an 889. It costs $12 IIRC. I have a few at home, but I didn't measure them yet. I'm using the data that John Krutke measured. Another plus is that the W2-880 has much lower distortion than the Aura NS2s that I'm using.

For a "real" unity the TBs are rather puny, but for a car, the small size is a bonus.

I'm curious why 532 Hz is the 'perfect score' when TD says 500 Hz, though obviously there is some wiggle room. FWIW, the ones I chose for 'M' before he scored the 'real deal' is the Fostex FF125K, which clocks in at ~533 Hz.

GM

__________________Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

It would be tiny, ~2x the front chamber Vb with it mounted flat against the horn. For open back, you'd need a ~500 Hz Fs driver with a mass corner slightly >1 kHz, ergo a large front chamber Vb with large vents, so not a viable option IMO since you'd need a Qes = ~0.05 to get the front Vb/vents down to ~where they need to be.

GM

__________________Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

The Fostex fe126e is close in specs and a little cheaper would this work also? I would worry that with the few very inexpensive drivers that you might end up having to buy a bunch to obtain drivers with the parameters needed so not much if any saving in the end. Regards Moray James.

I'm curious why 532 Hz is the 'perfect score' when TD says 500 Hz, though obviously there is some wiggle room. FWIW, the ones I chose for 'M' before he scored the 'real deal' is the Fostex FF125K, which clocks in at ~533 Hz.

GM

GM,

Every Unity will have a different target. To keep things simple, I decided to assign a "bullseye target" in my spreadsheet. It corresponds to John Sheerin's "perfect unity woofer", that's all.

For example, if you went with a BMS4540nd, you'd want a target that's an octave higher (1064hz). This would allow you to extend the high frequency response of the mid, taking some stress off the BMS. Of course it would also limit your low frequency extension!

If you used a monster compression driver like one of the TAD 2001s, you can get away with a target that's a full octave lower (266hz). This is because the TAD can live with a lower xover point. Of course, the $95 BMS is hard to beat in the top octave!

In a nutshell, your "target" will depend on your desired SPL level and your compression driver.

Aren't compromises a b1tch? This demonstrates that even if you spend $1000 for a compression driver, there will still be compromises. I hate to gush, but I think Danley has come up with one of the most elegant ways to mask these compromises. IMHO, a lot of newbies think that you can just throw money at the problem by purchasing the best drivers. This shows that driver selection is more important than the cost of those drivers.

I think Danley has come up with one of the most elegant ways to mask these compromises

Since I have been working on different implementations of the Unity concept for a while, I could not help myself from thinking about Tom's thought process while he was designing the first Unity. And, it seems to me, that there are not so many degrees of freedom as it appears.

First, the choice of a cross-over frequency is limited - at the low frequency range by the loading of the compression driver, and at the high frequency range by the physical limitations of the horn structure (e.g., the wall angle) and the dimensions of the mid-frequency drivers (one needs to be at about 1/4 wavelength), as well as the highest frequency that the mid-frequency drivers can reach on the horn.

Additionally, the bandwidth of the mid-frequency drivers is limited, I am afraid that 3 octaves is the maximum, again depending on the horn structure that will affect e.g., loading. This further influences the cross-over frequency choice if one wants a certain bandwidth with only a compression driver and mid-frequency drivers.

Please, do not misunderstand me; I think this is an ingenious concept. I just wonder if when Tom decided on performance goals the design did not just logically follow. However, perhaps I am just fooling myself and see the logic using hindsight and experiences of the many smart people who understood and discussed the Unity concept.